Liquid fuel burner



Aug. 28, 1962 R. G. HICKS LIQUID FUEL BURNER 2 Sheets-Sheet 1 Filed May 7, 1959 4 Iiil 6 w 1"! l 1 4 llillklllullnllllrlfllfillllll.

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INVENTOR ROBERT G. HICKS ATTORNEY Aug. 28, 1962 R. G. HICKS LIQUID FUEL BURNER 2 Sheets-Sheet 2 Filed May 7, 1959 INVENTOR ROBERT G. HlCKS FIG. IO

ATTORNEY United tates 3,051,229 LIQUID FUEL BURNER Robert G. Hicks, Bettendorf, Iowa, assignor to American Air Filter Company, Inc., Louisville, Ky, a corporation of Delaware Filed May 7, 1959, Ser. No. 811,621 8 Claims. (Cl. 158-91) This invention relates to vaporizing liquid fuel burners of the pot-type having a structural arrangement which, while affording superior operation with a gravity draft, is particularly directed to a pot-type burner adapted to receive a mechanical or forced draft air supply.

The basic structure of conventional pot burners is well known and often includes, at least in part, an upwardly open pot having a floor onto which liquid fuel is admitted and a perforated circumferential side wall through which air for vaporization and combustion purposes is ad mitted. The patent art discloses numerous structural elements and features such as baffles, central air supply tubes, canted and inclined air apertures, etc., which have been proposed for improving combustion and efliciency of these pot burners. While undoubtedly many of these innovations have, alone and in themselves, served to increase the efficiency of such pot burners to a degree, I am not aware that they have ever been arranged in such concert or combination to avoid substantially the considerable difliculty still encountered with carbon deposits in the form of soot and coke within these pots.

Thus, the object of the present invention is to provide a vaporizing pot-type burner having elements in a combination and arrangement that it will operate efficiently and tend to remain clean for extended periods.

Essentially, the invention contemplates: that a vaporization and combustion air supply tube be provided centrally within a pot which is nested within an outer shell, the pot having air inlet openings in its circumferential wall to permit the admission of part of the vaporization and combustion air from the annular space formed between the circumferential walls of the pot and shell; that a series of inverted skirt-like bafiles be disposed on the tube; thatthe walls of said tube be provided with air outlet apertures or holes to permit a part of the vaporization and combustion air to pass radially outwardly from the tube into the pot interior; and that the air openings in the circumferential wall of the pot be canted or given a particular direction to eifect a desired air circulation pattern. The particular arrangement of these elements will be specifically described in some detail in the following specification which is to be taken in connection with the accompanying drawing illustrating one embodiment of the invention, and wherein:

' FIGURE 1 is a somewhat diagrammatic view in the nature of a vertical section illustrating the relationship of the parts of a space air heater to which the subject invention may suitably be applied;

FIGURE 2 is a partly broken elevational view of the burner pot with the interior baflles also partly broken;

FIGURE 3 is a fragmentary detail view in elevation of a portion of the pot side wall with a forming tool in a rotated position in one air inlet opening of the bottom row thereof, this manner of illustration being utilized to more clearly show the degree to which each opening in that row, and the next row above, is canted from a horizontal plane;

FIGURE 4 is a horizontal sectional view along the line 44 of FIGURE 3, with the rotated position of the forming tool illustrating the degree to which the opening is canted from a vertical radial plane passing through the center of the pot and the opening;

7 FIGURE 5 is a fragmentary detail view in elevation of a portion of the pot side wall with a forming tool in a rotated position in one air inlet opening of the third from the bottom row thereof to show that each opening in that row is directed substantially horizontally;

FIGURE 6 is a horizontal sectional view along the line 6-6 of FIGURE 5, with the rotated position of the forming tool illustrating the degree to which the opening is canted from a vertical radial plane passing through the center of the pot and the opening;

FIGURE 7 is a fragmentary detail view in elevation of a portion of the pot side wall with a forming tool in a rotated position in one air inlet opening of the fourth from the bottom row thereof to show that each opening in that row is canted upwardly from a horizontal plane to the degree shown;

FIGURE 8 is a horizontal sectional view along the line 8-8 of FIGURE 7, with the rotated position of the forming tool illustrating the degree to which the openin is canted from a vertical radial plane passing through th center of the pot and the opening;

FIGURE 9 is a fragmentary detail view in elevation of a portion of the pot side wall with a forming tool in a rotated position in one air inlet opening of the fifth from the bottom row thereof to show that each opening in that row is directed upwardly and inwardly, but not tangentially;

FIGURE 10 is a vertical sectional View along the line 1010 of FIGURE 9;

FIGURE 11 is a fragmentary detail view in elevation of a portion of the pot side wall with a forming tool in a rotated position in one air inlet opening of the top row thereof to show that each opening in that row, and the row next below, is directed upwardly and inwardly, but not tangentially;

FIGURE 12 is a vertical sectional view along the line 1212 of FIGURE 11.

Referring to FIGURE 1 a space air heater of the type with which the present invention may be utilized includes a burner pot 2 concentrically nested within the cylindrical outer shell 4 to form a vertical annular space 6 between the circumferential or side walls of the pot and shell and a horizontal communicating passage 8 between the bottom walls of the pot and shell. A conduit 10 is provided so that a liquid hydrocarbon fuel may be supplied from a suitable source to the pot floor.

Fan 12 driven by a suitable motor 14 creates a ventilating air flow (indicated by heavy arrows) past the combustion chamber-heat exchanger 16 in heat transferring relationship and is discharged through outlet 18. Motor 14 also drives blower 20 which supplies vaporization and combustion air through duct 22 and an open-bottomed central tube 24 to the passageway 8 and annular chamber 6. This vaporization and combustion air is forced into the pot both from the central tube 24 and from the annular space 6 through apertures to be described hereinafter in some detail. The lighter arrows in FIGURE 1 indicate the direction and path of this air from the blower 20 to its ultimate discharge, as part of the products of combustion, from the combustion chamber 16 to atmosphere through stack 26. The illustration of air inlet apertures in the circumferential wall of the pot 2 has purposely been omitted and arrows substituted therefor to indicate the inclination of these apertures.

Within the lower part of the combustion chamber 16 an upwardly flared flame spreader 28 is concentrically mounted on the central tube 24 to spread the burning gases which rise out of the open top of the burner pot 2. Spaced below the flame spreader and well within the pot, a series of inverted skirt-like or upwardly flaring conical baffles 30, 32 and 34 are mounted in vertically spaced relationship on the central tube.

Referring now to both FIGURES 1 and 2, the air which is mixed with the fuel for combustion is introduced into the pot interior as indicated by the lighter arrows in FIGURE 1 through the circumferential wall apertures arranged in vertically spaced rows 36, 38, 40, 42, 44 and 46, and also through the central tube apertures also arranged in vertically spaced rows designated 48, 50 and 52 is ascending order, each row of the central tube apertures being disposed near the juncture of a battle mounted on the central tube.

Each of the bafiles 30, 32 and 34 is formed and mounted on the central tube so that the angle between the battle wall and tube wall approximates an angle between 4045. It will be noted that these 'baflles are shown as having different outside diameters, the lowest baflie 30 having the greatest outside diameter and the progressively higher baflles 32 and 34 having progessively smaller outside diameters.

As has been mentioned before, the air supplied to the pot for vaporization and combustion mixing purposes is introduced into the pot both through the circumferential wall apertures and through the central tube aper- Illaf.;g- 'Whllfl it is difiicult, if not impossible, to attempt to 'deli ne'ateihegeneral levels at which diflferent actions occur within the pot, for purposes of clarity in explanation the different rows of apertures in the pot circumferential wall will be characterized as: vaporization air aperturesrows 36 and 38; first primary air apertures row 40; second primary air aperturesrow 42; third primary air aperturesrow 44; secondary air apertures rows 46. The two lower rows of holes 48 and 50 in the central tube are believed to furnish mainly primary air, while the upper row 52 would most likely be characterized more properly as adding secondary air.

The pot wall apertures are given a particular direction and inclination by employing a forming tool 54 for canting the holes. Generally, these pot wall apertures are directed and inclined to cause the air which enters the vaporization air holes 36 and 38 to sweep downwardly and tangentially, the first primary air holes 40 being directed tangentially only, the second primary holes 42 being directed tangentially and upwardly, and the third primary air holes 44 being inclined upwardly only.

As illustrated in FIGURES 3 and 4 each vaporization air aperture in rows 36 and 38 is directed downwardly at an angle of about 40 below the horizontal, and is directed tangentially at an angle of about 65 from a vertical radial plane.

As illustrated in FIGURES 5 and 6 each aperture in the first primary air row 40 is directed generally horizontally, and is directed tangentially at an angle of about 65 from a vertical radial plane.

As illustrated in FIGURES 7 and 8 each aperture in the second primary air row 42 is directed upwardly at an angle of about 40 above a horizontal plane, and is directed tangentially at an angle of about 65 with a vertical radial plane. 7

As illustrated in FIGURES 9 and 10, each aperture in the third primary air row 44 is directed upwardly at an angle about 65 relative to a horizontal plane, and has no tangential component. a As illustrated in FIGURES 11 and 12, each secondary air aperture in rows 46 is directed upwardly at an angle of about 50 relative to a horizontal plane, and has no tangential component.

In the operation of the apparatus embodying the invention, the liquid hydrocarbon introduced through conduit .10 to the floor of the burner pot 2 is ignited either manually or by automatic means. After ignition, combustion is sustained so long as fuel and combustion air in the proper proportions are supplied to the pot, the radiated heat from the combustion in the upper part of the pot and the combustion chamber 16 serving to help vaporize additional fuel which flows into the pot.

The major part of the forced draft vaporization and combustion air delivered by blower 20 to tube 24 enters the pot through the pot wall apertures 36-46 while a operation.

minor part enters through the air tube apertures 4852. As is known in the art, the total open area of the apertures through which such air is introduced is determined in accordance with the rate at which fuel is to be burned.

While it is diificult to describe, with any assurance of accuracy, exactly how the superior mixing and combustion process is obtained with the present invention, the parts the various described elements are believed to play will be explained.

In the lower zone of the pot, the vaporization air holes admit air which is directed against the surface of the fuel and which, as it sweeps along in a circular path, mixes with the vaporized fuel. It will be understood that part of the heat causing vaporization is contained within the vaporizing air jets entering the pot through holes in rows 36 and 38, the heat having been picked up by the air in its passage through the heated central tube, and part of the vaporizing heat is derived from the radiated heat from above. However, the temperature of this vaporized fuelair mixture is well below its cracking temperature since this lower zone is substantially shielded by the bafiles from the radiated heat from above. As this mixture swirls and moves upwardly in the space between the periphery of baflie 30 and the pot wall, additional heated air from first primary air holes 40 is directed tangentially into the pot. The mixture with added air also swirls upwardly and still more air from second and third primary air holes 42 and 44, and from central air tube holes 48 and 50, are added to the mixture. As this fuel and air mixture swirls upwardly past the outer periphery of the baflle 30, and additional primary air is added, the exposure of this mixture to the radiated heat from above is increased since the progressively higher baffles have progressively decreased radii. Thus, the primary air is progressively increased at, progressively higher mixture temperatures so that complete, or substantially complete hydroxylization of the fuel is effected. When this hydroxylized fuel passes upwardly out of the pot with the addition of secondary air from holes 46 and 52, the burning process is accomplished with minimized carbon deposits in the pot and combustion chamber.

As mentioned before, the baflies 30, 32 and 34 serve to shield the vaporization zone from radiated heat and permit increased exposure to the ascending mixture. However, they further serve, in cooperation with the air from central tube holes 48, 50 and 52, in preventing eddy currents of the mixture from flowing radially inwardly and downwardly along the periphery of the central tube. Such eddy currents contribute to precipitation of carbon on the central tube wall which is at a much lower temperature than the mixture.

While there is some leeway in relative locations of the structural elements, certain relationships provide superior 7 Thus, for example, it is preferred that the first, second and third primary air hole rows 40, 42 and 44 be spaced slightly below the upper rim of the lower, middle, and upper baffles 30, 32 and 34 respectively. It is further preferred that the central tube air hole rows 48, '50 and 52 be closely adjacent the junctures of the tube and respective bafiles. It is not necessary that the central air tube holes be canted. The preferred degree of inclination of the air holes in the circumferential wall of the illustrated pot (which is based on a commercial pot of 13" diameter and 7" height) is stated in the foregoing description. While in the manufacture of this pot a :2" tolerance is maintained, a variation of as much as :5 permits satisfactory operation.

The illustrated 13" burner can be operated with relatively little carbon deposit at a maximum rate of over 3 gallons of fuel per hour and at a minimum rate of less than 2 gallons per hour. Smaller pots of 11 /2" and 10" diameter and a height of 5 1 may be operated at lower fuel rates. In the smaller versions, only one row of vaporization air holes is provided, the preferred angle of elevation from a horizontal plane of the second primary air holes is 27, and of the secondary air holes is 62. The preferred tangential canting of the holes of the smaller version is within 3 of the corresponding holes of the larger pot.

Having described my invention, I claim:

1. A liquid fuel burner of the type adapted to receive a forced draft combustion air supply, comprising: an up wardly open burner pot including a bottom wall provided with a central opening and a circumferential wall having a plurality of vertically spaced rows of air inlets in communication with said air supply for admitting air into said pot interior; a centrally disposed air tube extending upwardly from said central opening and a plurality of upwardly flaring bafiies disposed concentrically in vertically spaced relation to project outwardly from said tube below the upper end of said pot, each successively higher baflle projecting radially outwardly less than the bafile immediately below, the space between said air tube and said pot circumferential wall being substantially unobstructed except for said baflies; and means defining air outlets in said air tube for directing air against the upper surfaces of said baffles.

2. The liquid fuel burner of claim 1 wherein: said rows of circumferential wall inlets include at least one lower row having said inlets canted downwardly and tangentially, at least one intermediate row having said inlets canted upwardly and in the same general tangential direction as said lower row inlets, and at least one upper row having said inlets directed upwardly only.

3. The liquid fuel burner of claim 1 wherein: said air outlet means in said air tube includes a plurality of vertically spaced rows of air outlets; and, each of said baflles is disposed with its inner rim closely below one of said rows of air outlets and with the major portion of the upper surface of said baffle extending above the level of said row.

4. A liquid fuel burner of the type adapted to receive a forced draft combustion air supply, comprising: an up wardly open burner pot having an apertured circumferential wall and a bottom wall provided with a central opening; a vertical air tube receiving said air supply at its upper end and extending downwardly through said pot, the open bottom of said tube being received by said central opening; wall means providing a radially outwardly extending passage way from said open bottom to an enenclosed space surrounding said apertured circumferential wall so that the air passing downwardly through said open bottom is directed outwardly to said space for admission to said pot through said apertured circumferential Wall; and a plurality of upwardly flaring skirt-like baflles disposed concentrically in spaced superposed relation to project outwardly from said tube below the open upper end of said pot, each successively higher bafile projecting radially outwardly less than the bafile immediately therebelow, the space between said tube and said pot circumferential wall being substantially unobstructed except for said bafiies; and air outlet means in said tube for directing air from said tube against the upper surfaces of said bafiles.

5. The liquid fuel burner of claim 4 wherein: said air outlet means includes a plurality of vertically spaced rows of air outlet means in the wall of said air tube, each row of said air outlet means being disposed closely above the juncture of a corresponding battle on said tube so that air discharged radially outwardly from said tube through said air outlet means flows along the upper surface of said baffies.

6. The liquid fuel burner of claim 5 wherein: said apertured circumferential wall includes a plurality of vertically space rows of apertures with the rows in the lower portion of said wall being canted to impart a circular motion to the air passing therethrough, and with the rows in the upper portion of said wall being inclined upwardly and inwardly.

7. A liquid fuel burner comprising: an upwardly open pot having a circumferential wall provided with a plurality of vertically spaced rows of air inlets including at least one vaporization air row having said inlets directed downwardly and tangentially, a first primary air row having said inlets directed tangentially, a second primary air row having said inlets directed upwardly and tangentially, a third primary air row having said inlets directed upwardly, and at least one secondary air row having said inlets directed upwardly; a central air tube in said pot and having its lower end in communication with said air inlets in said circumferential wall, said tube including in its wall a lower, intermediate, and upper row of air outlets; and a plurality of upwardly flaring bafiles mounted on said tube with each successively higher bafile projecting radially outwardly less than the bafiie immediately below to provide a progressively increased annular space between the periphery of succemively higher baflles and said circumferential wall, the lowest of said baffles having its lower rim closely below said lower row of air outlets and its upper rim above the level of said first primary air row, the next successively higher baffie having its lower rim closely below said intermediate row of air outlets and its upper rim above the level of said secondary air row, and the next successively higher baflie having its lower rim close- 1y below said upper row of air outlets and its upper rim above the level of said third primary air row.

8. The liquid fuel burner of claim 7 wherein: said baflles are inclined upwardly at approximately 45 from a horizontal plane.

References Cited in the file of this patent UNITED STATES PATENTS 2,184,653 Sherrick et al Dec. 26, 1939 2,561,934 Mayo July 24, 1951 FOREIGN PATENTS 522,515 Canada Mar. 13, 1956 550,970 Belgium Sept. 29, 1959 

